Curing agents for chlorosulfonated polyethylene



Patented Nov. 17, 1953 CURING AGENTS FOR CHLOROSULFO- NATED POLYETHYLENEOrrin G. Youngquist, Malcolm A. Smock, and Richard E. Brooks,Wilmington, Del., assignors to E. I. du Pont de Nemours & Company,Wilmington, Del., a corporation of Delaware No Drawing. ApplicationMarch 23, 1951, Serial No. 217,312

5 Claims. (Cl. 260-41) This invention relates to a process for thepreparation of synthetic elastomers from substituted saturated polymersand more particularly relates to the preparation of elastomers, tocarbon black, for cross-linking saturated and substituted polymers togive elastomers, and especially to channel black for cross-linking thechlorosulfonated polymers of ethylene.

The McQueen U. S. Patent 2,212,786, issued August 27, 1940, describes aprocess for the preparation of chlorosulfonated olefin polymers andespecially the chlorosulfonated products of normally solid polymers ofethylene. The process of the McQueen patent is applicable to thechlorosulfonation of other saturated polymers such, for example, aspolyisobutylene, Fischer-Tropsch hydrocarbons, the polymethylenes, thepolyacrylonitriles and others. In the McAlevy et a1. U. S. Patent2,416,061, issued February 18, 1947, there is described a process ofcuring hydrocarbon and oxygenated hydrocarbon polymers which have beenchlorosulfonated in accord with the process of the McQueen patent. TheMcAlevy et al. patent, in addition to the chlorosulfonation reaction,describes other reactions giving products that can be cured and therebyconverted to elastomers. In order to produce such products the patenteesstate that polymers should carry at least two substituent groups. Thosethat impart (1) Elastic properties provided by:

A--Halogen, BHydrocarbon and C-Acyloxy groups;

(2) An those that make it possible to cure the product, provided by:

ASulphonating,

B--Phosphonating,

C-Carboxylating,

D-Chlorosulionating, E-Chlorophosphonating, F--Chloroearboxylating, and

G-Agents that give a hydrogen sulfide group.

2 ties and substituents that impart curing ability to hydrocarbonpolymers, to provide improved cross-linked chlorosulfonated solidpolymers of ethylene and to provide as cross-linking agents forms ofcarbon black for treating compounds containing chloride and sulfonylchloride groups, they are, inter alia, the objects of the invention.

The above and other objects are realized in accord with the invention bycertain forms of carbon black used for curing and/or cross-linkingsaturated hydrocarbon polymers that have been substituted with halogen,hydrocarbon, or acyloxy groups and also have been substituted withsulphonating, phosphonating, carboxylating, chlorosulfonating,chlorophosphonating, chlorocarboxylating groups or agents that give ahydrogen sulfid group. More particularly these forms of carbon black areespecially active in cross-linking th chlorcsulfonated saturatedhydrocarbons and especially those produced from the substituted solidpolymers of ethylene containing from 20% to 45% by weight of chlorineand from 0.25% to 3.0% by weight of sulfur.

In addition to the substituted saturated hydrocarbon polymers describedin the McQueen and McAlevy et a1. patents supra, it has been found thatother substituted hydrocarbon polymers are their equivalents, namelysimilarly substituted and especially chlorosulfonated; polyisobutylene;

'Fischer-Tropsch hydrocarbons; polymethylenes,

hydrogenated diolefin polymers; hydrogenated diolefin styreneinterpolymers; hydrogenated rubber; alkyd resins; neoprene; hydrogenatedpolymers produced by the interaction of butadiene with xylene, tolueneand similar aromatic hydrocarbons; and equivalent substituted saturatedhydrocarbon polymers. Moreover, the curing and/or cross-linking agentsare likewise useful for treating the following polymers which have beensubstituted in accord with the process of the McAlevy et a1. patent:hydrogenated diolefin-acrylonitrile, -acrylates, -methacrylateinterpolymers; polyacrylic and polymethacrylic acid esters; polyvinylacetate; polyvinyl chloride; polyvinylidene chloride; and the like.

The process of the invention is conducted by mixing thoroughly thecuring and/or cross-linking agent with the substituted polymer followedby subjecting the mixture to heat and pressure. Thorough incorporationof the curing and/or cross-linking agent into the substituted polymer isaccomplished by passing the mixture through the rolls of a rubber millor the agents may be mixed with the substituted polymer in a suitablemachine, such as a Banbury mixer, and the resulting product subsequentlyheated and subjected to pressure for conversion to the cured elastomer.The agents are mixed with the substituted polymers in amounts rangingfrom 2 to ing of the polymer substantially constant from one run to thenext. The resulting stock was then sheeted out, molded and press cured.

Examples 1 to 8 of the table illustrate the cross- 120 parts by weightof the cross-linking agent per linking ability of carbon blacks in thepresence 100 parts of th substituted polymer. The preor in the absenceof sulfur and addition agents ferred amount of cross-linking agent usedis beon chlorosulfonated and on chlorinated polymers tween 10 and 60parts by weight per 100 parts of of ethylene. Barium sulfate, which isan inert th s bstituted polymer. material with no significant curing orcross-link- Compounding agents are added with the cross- 10 inginfluence on the chlorosulfonated polymer of linking agent if desiredand for this purpose ethylene, is used in Example 1 for comparativemonobasic or polybasic acids of high molecular purposes. The superiorityof channel black over weight are used, such as stearic acid, palmiticfurnace black is seen from a comparison of the acid, rosin and the like.Small amounts of antiphysical properties of Example 4 with those ofoxidants and/or accelerators can be used with Examples 2 and 3. Channelblack is a better advantage, such as diphenylguanidine,mercapcross-linking agent than furnace blacklalthough tobenzothiazole,tetramethyl thiuramdisulfide, for many purposes the products of Examples2 phenyl beta-naphthyl amine or high molecular and 3 are superior. Theuse of sulfur together weight phenolic antioxidants. These agents arewith carbon black is illustrated by Examp es 5 used to give from 1 to 5%thereof, based on the 0 8, the amount of the carbon black used beingweight of the substituted polymer. Fillers, pigbut parts while 160 Partswere used in Exments and other agents, such as barium sulfate, amples 3and 4. Good cures, however, were obkaolin, diatomaceous earth, powderedtalc, titained by the process of Examples 5 and 7 in tam'um dioxide,calcium sulfate and the like im which no sulfur was present. prove theproducts for certain purposes. Sulfur 25 The polymeric elastomersproduced in accord is used, if it is desired, to make the polymer morewith the process of this invention are superior elastic and increasetensile strength, for which in y respects to Vulcanized rubber and Dpurpose 2.5 to 15 parts per 100 parts by weight tiwlarly in theseimportant properties Which of t tit t polymer are dd d, Th bclude heatresistance, water resistance, abrasion stituted polymers, after thadditi n of r sresistance, resistance to oxidation, resistance tolinking agents, whether or not they are comhydrocarbon oils, resistanceto breakage by flexpounded with the antioxidants, fillers and the n fatiu resistance n resistance to discollike described above, are cured byheating at a oration and Organic instability. Moreover, t e temperaturebetween 25 and 175 C. for a period Pr duc s pr du ed with the curingan/or crosspreferably in the order of 10 to 120 minutes linking agentshereinbefore described are likeunder a pressure of from 25 to 1500lbs/sq. inch. wise suitable for use in the art n 3 to Vulcanization,however, will take place at lower Place, in many instances, rubber butalso o p temperatures, pressures and longer rates, alvide pr s superiorin many p ta t rethough, contrariwise, a fraction of a second in pe tsto products made from rubber. certain instances, for example when steamis We claim: present, is suflicient. Shaped articles can be pro- Aprocess for the pr a on of cured elasduced by curing the compoundedchlorosulfotomers which consists of heating a chlorosu1fonated polymersdirectly in a mold having the a d hydrflearbon p y at a e pe tu bdesired shape. tween 25 and 175 C. and under a pressure up The exampleswhich follow illustrate preferred t0 1 1 qf r fr m a fraction of aminembodiments of the invention in which parts are e o minutes in the pe c of channel by weight unless otherwise indicated. black.

TabZeI Parts by Weight Example 1 2 3 4 5 6 7 8 Polymer 200 200 200 200100 100 100 100 B11804 33s Furnace black- 134' 160 25 25 Channel black160 25 25 TetroneA 2- 2 Staybelite resin 3 Stearic acid 2 2 2 2 Sulfur1o 10 1o 10 Temperature, C 135 135 135 135 160 160 160 Time (minutes) 9090 60 60 60 PHYSICAL PROPERTIES Tensile p. s. i. (initial) 200 415 6651,640 I 1, 425 625 1,275 1, 600 100% modulus (initial) 175 415 660 1,315175 115 315 400 Percent elongation (initial) 460 275 200 385 665 415 275Percent residual elongation 120 75 -50 15 25 108 25 1 Chlorosullonatedpolymer of ethylene-27% Cl-l.9% S. 2Dipcntamcthylenethiuramtetrasulfide. 1 Hercules Powder O0.Hydrogenatc lwood rosin.

'. The procedure employed in carrying out the processes of the exampleswas to mill the polymer, filler and/or curing agents together on a 6inch rubber mill, maintaining the volume load- 2. A process for thepreparation of cured elastomers which consists of heating achlorosulfonated normally solid polymer of ethylene at a temperaturebetween 25 and C. and under a pressure between 25 and 1500 lbs/sq. in.for Irorn 10 to 120 minutes in the presence of channel black.

3. The process of claim 2 conducted in the presence of from 2 to 120parts by weight of channel black per 100 parts of the polymer.

4. A process for the preparation of cured elastomers which consists inheating a chlorosultonated normally solid polymer of ethylene containingfrom 20 to 45% by weight of chlorine and from 0.25 to 3.0% by weight ofsulfur at a temperature between 25 and 175 C. and under a pressure up to1500 lbs/sq. in. for from a. fraction of a minute to 120 minutes in thepresence 0! channel black.

5. The process of claim 4 conducted in the 6 presence of from 2 to 120parts by weight of channel black per 100 parts of the polymer.

' ORRIN G. YOUNGQUIST. MALCOLM A. SMOOK. RICHARD E. BROOKS.

References Cited in the file of this patent UNITED STATES PATENTS NameDate McAlevy et a1. Feb. 18, 1947 OTHER REFERENCES Du Pont RubberChemicals," Report 43-1, pages 39 and 40, published by Rubber ChemicalsNumber 15 Division of E. I. du Pont de Nemours I: 00., W11- mington,Delaware, February 1943.

1. A PROCESS FOR THE PREPARATION OF CURED ELASTOMERS WHICH CONSISTS OFHEATING A CHLOROSULFONATED HYDROCARBON POLYMER AT A TEMPERATURE BETWEEN25 AND 175* C. AND UNDER A PRESSURE UP TO 1500 LBS./SQ. IN. FOR FROM AFRACTION OF A MINUTE TO 120 MINUTES IN THE PRESENCE OF CHANNEL BLACK.